This study is primarily aimed at transplanting tissues containing catecholamines or L-DOPA, including adrenal medulla, tumor cells, genetically altered cells, and embryonic brain tissue, into the brain. Its purpose is to elucidate the properties of these tissues after transplantation and to elucidate the response of the host brain to the transplanted tissues. Specifically, these experiments employ nonprimate animal models to (1) develop the techniques of brain tissue transplantation for clinical use in Parkinson's disease; (2) develop brain tissue transplantation techniques so they eventually may be applicable to other disorders, such as schizophrenia and epilepsy, if and when these disorders become sufficiently understood to permit such applications; and (3) elucidate factors that control brain development and responses of the brain to injury or impairment, with particular emphasis on the nigrostriatal dopamine system. During the past reporting year, significant progress has been made in these areas.